^% 



THE ART OF INVENTING 



BY 



EDWIN J. PRINDLE, M-E*, L.L*M., 
of the New York Ban 



i 



A paper read at the 23d Annual G>nvention of the American Insftitute of 
Electrical Engineers, Milwaukee, "Wis,, May 28-3), J906. 






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A paper presented at the 23d Annual Conven- 
tion of the American Institute of Electrical 
Engineers, Milwaukee, IVis., May 28-31, 1903. 

Copyright 1906. By A. I. E. E. 



THE ART OF INVENTING. 



BY EDWIN J. PRINDLE. 



There are many kinds of invention. The poet, the artist, 
the playwright, the novehst all exercise or may exercise in- 
vention in the production of their works. The merchant may 
exercise invention in the devising of a new method of selling 
goods. The department store was an invention of this class. 

The subject of my paper is, however, the art of making tech- 
nical inventions, and particularly patentable inventions. And, 
first, of its commercial importance; for the engineer is con- 
cerned with things having a commercial value. By the art of 
inventing, wealth is created absolutely out of ideas alone. It 
usually takes capital to develop an invention and make it pro- 
ductive, but not always. A notable recent example is Professor 
Pupin's loaded telephone line. He received a very large sum 
of money, and his expenditures, as I understand, were com- 
paratively trivial. 

The certificate of ownership of an invention is a patent, and 
the importance of the art of invention will be made apparent 
from a brief consideration of what rights a patent confers and 
of the part that patents play in the industries. 

A patent is the most perfect form of monopoly recognized 
by the law. As was said in a recent decision: 

" Within his domain, the patentee is czar. The people must take 
the invention on the terms he dictates or let it alone for seventeen years. 
This is a necessity from the nature of the grant. Cries of restraint of 
trade and impairment of the freedom of sales are unavailing, because 
for the promotion of the useful arts the constitution and statutes author- « 
ize this very monopoly." 

465 



466 PRINDLE: THE ART OF INVENTING. [May 30 

There is an enormous amount of wealth in this country that 
is based upon patents. As an instance, might be mentioned 
the fact that the United Shoe Machinery Company is, by means 
of patents, able to control the sewing machines upon which 
ninety per cent, of the welt shoes in the United States are 
sewed. The Bell Telephone Company, and the Westinghouse 
Air Brake Company and many other corporations of the first 
importance built themselves up on patents. Patents have be- 
come so well recognized a factor in commerce that, in many 
lines of manufacture, concerns do not depend simply upon 
cheapness of manufacture, or quality of product, to maintain 
their trade, but they count on always having a product which 
is at least slightly better than that of their competitors, and 
which is covered by patents, so that they do not have to com- 
pete with an article of equal merit. And they keep a corps 
of inventors at work in a constant effort to improve the product, 
so that, when the patents now giving protection have expired, 
they will have a better article to offer, which shall also be pro- 
tected by patents. 

Inventing has become almost a recognized profession. Many 
large concerns constantly employ a large corps of inventors, 
at liberal salaries. Besides the inventors employed by large 
corporations, there are many inventors who have maintained 
their independence, and are free lances, so to speak. Some in- 
ventors have become wealthy almost solely by their inventions, 
such as Edison, Bell, Westinghouse, Marconi, Pupin, Tesla, 
and Sprague. A considerable number of the smaller manufac- 
turing concerns are built largely or wholly upon the inventions 
of their principal owners. 

Aside from the question of financial returns from inventing, 
the inventor has the satisfaction of knowing that he is a pro- 
ducer of the most fundamental kind. All material progress 
has involved the production of inventions. Inventors are uni- 
versally conceded to be among the greatest benefactors of the 
human race. 

The art of invention is therefore one of great commercial 
and economical importance, and it becomes a matter of much 
interest to know how inventions are produced. It is my ob- 
ject to attempt an explanation of the manner of their produc- 
tion. 

• If it be inquired on what grounds I offer an explanation of 
this apparently most difficult subject, I reply that, in the prac- 



1906.] PRINDLE: THE ART OF INVENTING. 467 

tice of patent law, I have often had occasion and opportunity 
to inquire into the mental processes of inventors, and that 
the subject is one to which I have given considerable attention. 

It seems to be popularly believed that the inventor must 
be born to his work, and that such people are born only occa- 
sionally. This is true, to a certain extent, but I am convinced 
there are many people who, without suspecting it, have latent 
inventive abilities, which could be put to work if they onl}^ 
knew how to go about it. The large percentage of inventors 
in this country compared with all other countries, shows that 
the inventive faculty is one which can be cultivated to some 
extent. The difference in ingenuity is not wholly a matter of 
race, for substantially the same blood exists in some other 
countries, but it is the encouragement of our patent laws that 
has stimulated the cultivation of this faculty. 

The popular idea seems to be that an invention is produced 
by its inventor at a single effort of the imagination and com- 
plete, as Minerva sprang full grown and fully armed from the 
mind of Jove. 

It is, undoubtedly, true that every inventor must have some 
imagination or creative faculty, but, as I shall seek to show, 
this faculty may be greatly assisted by method. While reason- 
ing does not constitute the whole of an inventive act, it can, 
so to speak, clear the way and render the inventive act easier 
of accomplishment. 

Invention has been defined as "In the nature of a guess;' 
the mind leaps across a logical chasm. Instead of working 
out a conclusion, it imagines it." The courts have repeatedly 
held that that which could be produced purely by the process 
of reasoning or inference, on the part of -one ordinarily skilled 
in the art is not patentable, but that the imaginative or creative 
faculty must somewhere be used in the process. The mind^ 
must somewhere leap from the known to the unknown by means 
of the imagination, and not by mere inference in making the 
invention. But the inventor, consciously or unconsciously, by 
proper method, reduces the length of this leap to much more 
moderate proportions than is popularly supposed. 

That reasoning and research frequently enter very largely 
into the inventive act in aid of the creative faculty is the opin- 
ion of Dr. Trowbridge, of Columbia University who said: 

'^" Important inventions leading to widespread improvements in the 
arts or to new industries do not come by chance, or as sudden inspira- 



46S PRIXDLE: THE ART OF IXVEXTLXG. [May 30 

tion, but are in almost every instance the result of long and exhaustive 
researches by men whose thorough familiarity with their subjects en- 
ables them to see clearly the way to improvements. Almost all im- 
portant and successful inventions which have found their way into gen- 
eral use and acceptance have been the products of well-balanced and 
thoughtful minds, capable of patient laborious investigation." 

Judge Dnimmond, in a decision many years ago, said: 

" Most inventions are the result of experiment, trial, and effort, and 
few of them are worked out by mere will." 

Most inventions are an evolution from some previously in- 
vented form. It has been said: 

" We know exactly how the human mind works. The vmknown — or 
unknowable — it always conceives in terms of the known." 

Even the imagination conceives in terms of what is already- 
known; that is, the product of the imagination is a transforma- 
tion of material already possessed. Imagination is the associa- 
tion in new relations of ideas already possessed by the mind. 
It is impossible to imagine that, the elements of which are not 
already known to us. We cannot conceive of a color which 
does not consist of a blending of one or more colors with which 
we are already familiar. This evolution of an invention is 
more or less logical, and is often worked out by logical pro- 
cesses to such an extent that the steps or efforts of imagination 
are greatly reduced as compared with the effort of producing 
the invention solely by the imagination. 

Edison is quoted as having said that " any man can become 
an inventor if he has imagination and pertinacity," that " in- 
vention is not so much inspiration as perspiration." 

There are four classes of protectable inventions. These are 

Arts, 

Machines, 

Manufactures, and 

Compositions of matter. 

In popular language an art may be said to be any process 
or series of steps or operations for accomplishing a physical 
or chemical result. Examples are, the art of telephoning by 
causing undulations of the electric current corresponding to 
the sound waves of the spoken voice. The art of casting car 
wheels, which consists in directing the metal into the mold in 
a stream running tangentially instead of radially, so that the 
metal in the mold is given a rotary movement, and the heavy, 
sound metal flows out to the rim of the wheel, while the Hght 



1906.] P KINDLE: THE ART OF INVENTING. 469 

and defective metal is displaced toward the centre, where it is 
not subjected to wear. 

The term machine hardly needs any explanation. It may 
be said to be an assemblage of two or more mechanical elements, 
having a law of action of its own. 

A manufacture is anything made by the hand of man, which 
is neither a machine nor a composition of matter; such as, a 
chisel, a match, or a pencil. 

The term composition of matter covers all combinations of 
two or more substances, w^hether by mechanical mixture or 
chemical union, and whether they be gases, fluids, powders or 
solids; such as, a new cement or paint. 

These definitions are not legally exact, but serve to illustrate 
the meaning. 

In the making of all inventions which do not consist in the 
discovery of the adaptabilit}^ of some means to an end not 
intentionally being sought after, the first step is the selection 
of a problem. The inventor should first make certain that the 
problem is based upon a real need. Much time and money 
is sometimes spent in an effort to invent something that is not 
really needed. What already exists is good enough or is so good' 
that no additional cost or complication would justify anything 
better* The new invention might be objectionable because it 
would involve counter disadvantages more important than its 
own advantages, so that a really desirable object is the first 
thing to be sure of. 

Having selected a problem, the next step should be a thorough 
analysis of the old situation, getting at the reasons for the 
faults which exist, and in fact discovering the presence of 
faults which are not obvious to others, because of the tendency 
to believe that whatever is, is right. 

Then the qualities of the material, and the laws of action 
under which one must operate should be exhaustively considered. 
It should be considered whether these laws are really or only 
apparently inflexible. It should be carefully considered whether 
further improvement is possible in the same direction, and such 
consideration will often suggest the direction in which further 
improvement must go, if a change of direction is necessary. 
Sometimes the only possible improvement is in an opposite 
direction. A glance at the accounts of how James Watt in- 
vented the condensing steam-engine will show what a large 
part profound study of the old engine and of the laws of steam 



470 PRIXDLE: THE ART OF IXVEXTIXG. [May 30 

played in his invention, and how strongly they suggested the 
directions of the solutions of his difficulties. 

We now come to the constructive part of inventing, in order 
to illustrate which, I will seek to explain how several inventions 
were, or could have been, produced. 

The way in which the first automatic steam engine was pro- 
duced was undoubtedly this — and it shows how comparatively 
easily a really great invention may sometimes be made. It 
was the duty of Humphrey Potter, a boy, to turn a stop-cock 
to let the steam into the cylinder and one to let in water to 
condense it at certain periods of each stroke of the engine, and 
if this were not done at the right time, the engine would stop. 
He noticed that these movements of the stop-cock handles took 
place in unison with the movements of certain portions of the 
beam of the engine. He simply connected the valve handles 
with the proper portions of the beam by strings, and the engine 
became automatic — a most eventful result. 

As one example of the evolution of an invention, I will take 
an instrument for measuring and recording a period of time, 
known as the calculograph, because it lends itself with facility, 
to an explanation from a platform and because my duties as a 
lawyer have necessitated my becoming very familiar with the 
invention, and have caused me to consider how it was probably 
produced. 

And first the problem: There was much occasion to determine 
and record the values of periods of elapsed time; such as, the 
length of time of a telephone conversation; as the revenue of 
the telephone companies depended upon the accuracy of the 
determination. All the previous methods involved the record- 
ing in hours and minutes the times of day marking the initial 
and the final limits of the period to be measured, and then the 
subtraction of the one time of day from the other. This sub- 
traction was found to be very unreliable as well as expensive. 
The problem then was to devise some way by which the value 
of the period could be arrived at directly and without sub- 
traction and also by which such value could be mechanically 
recorded. 

The prior machine from which the calculograph w^as evolved 
is the time-stamp, a printing machine having a stationary die 
like a clock dial and having a rotating die like the hand of the 
clock, as in Fig. 1. The small triangle outside the dial is the 
hour hand, it being placed outside the dial because it is necessary 



190G.] PRINDLE: THE ART OF INVENTING. 471 

that the two hands shall be at the level of the face of the dial and 
yet be able to pass each other. The hour hand may be dis- 
regarded here, as the records needed are almost never an hour 
long. The manner of using the time stamp to determine the 
value of an interval was to stamp the time of day at the be- 
ginning of the period, and then to stamp the time of day at the 
close of the period at another place on the paper, as shown 
in Fig. 2, and finally mentally to subtract the one time of day 
from the other to get the value of the period. 

The inventor of the new machine conceived the idea that, 
if the time-stamp were provided with guides or gauges so that 
the card could be placed both times in the same position, and 






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Fig. 1. 
Time Stamp Record. 



the two records of the time stamp thus be superimposed con- 
centrically (as illustrated in Fig. 3), the value of the period 
would be represented by the arc marked off by the initial and 
final imprints of the minute hand, so that, instead of sub- 
tracting one record from another, he had only to find the value 
of the arc marked off by counting the corresponding number 
of minutes along the dial. 

The inventor had thus gotten rid of the subtraction, but there 
were several desirable qualities not yet obtained. First, he 
could not tell from the record alone, whether it was the longer 
or the shorter arc marked off that was the measure of the period. 
For instance, he could not tell whether the period was 7 or 
53 minutes. This was because the two hand or pointer im- 



472 PRINDLE: THE ART OF INVENTING. [May 30 

prints were exactly alike except in position. So he conceived 
the idea of making the pointer imprints different in appearance, 
by providing the pointer die with a mark in line with the pointer, 
as illustrated in Fig. 4. 

The mark and pointer revolve together and either the dies 
or the platen are so arranged that the mark can be printed 
without the pointer at the initial imprint and the pointer 
at the final imprint as in Fig. 5, the mark being printed or 
not at the final imprint, as desired. This could be done either 
by allowing the pointer die or the corresponding portion of 
the platen to remain retracted from the paper during the first 
printing. 

<V ''" / <V ^" f 



M 



Mm - 



' lA ' lA ' 

9:23 Fig. 2. 10:15 

Initial Time Stamp Record. Final Time Std.mp Record. 

Elapsed Time: 10:15— 9:23 = 52 minutes. 
To read this record, hours and minutes must be subtracted from 
hours and minutes, an operation liable to much error. 

It could thus be told with certainty from the record alone 
whether the longer or the shorter arc is the measure of the 
period, because the beginning of the arc is that indicated by 
the imprint of the mark without the pointer. 

There was still something to be desired. The counting of 
the minutes along the measuring arc was a waste of time, if 
the value of the arc could in some way be directly indicated. 
If the hand were set back to 12 o'clock for the initial imprint, 
the final imprint would show the hand pointing directly at 
the minute whose number on the dial is the value of the period' 
and it would not even be necessary to count. But the setting 



1906.] PRNIDLE: THE ART OF INVENTING. 473 

of the hand back to zero would prevent its making the final 
imprint of any previously begun record, so that the machine 
could only be used for one record at a time. It was desirable 







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Fig. 3. 

Subtraction eliminated but counting still required and uncertainty 

whether elapsed period is 7 or 53 minutes. 

to have a machine that would record any number of overlapping 
intervals at the same time, so that one machine would record 
the intervals of all the telephone conversations under the 
control of a single operator, or rather of two operators, because 

;. XII 

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Fig. 4. 
Hand and zero mark revolving within stationary dial. 

both of them could reach the same machine. So it wouldn't 
do to set the hand back to zero, as the hand must rotate con- 
stantly and uniformly. Then why not set the zero up to the 



474 PRIXDLE: THE ART OF IXVEXTIXG. [May 30 

hand at each initial imprint? This meant making the dial 
rotatable, as well as the hand. It gave an initial record like 
that shown in Fig. 6. 

The inventor then thought of securing the dial to the pointer 
die so that they would revolve together, the zero of the dial 
being in line w4th the pointer, as illustrated in Fig. 7. This 
would obviate the necessity of setting the zero of the dial up 
to the pointer at the initial imprint. 

But again the improvement involved a difficulty. As the 
dial rotated, its final impressions would never register with its 
initial impressions and would therefore always destroy them. 
As the first imprint of the dial was the only useful one, and as 






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Fig. 5. 
Initial imprint of zero mark alone and final imprint of hand (and 
zero). Elapsed time, S minutes. No subtraction and no uncertainty 
as to Avhich imprint first, but counting still required. 



the second imprint only made trouble, the inventor conceived 
the idea of not making any imprint of the dial at the close of 
the period, and this he accomplished by making the annular 
portion of the platen covering the dial so that it could be ad- 
vanced to print or not as desired. As the zero of the dial 
always marked the beginning of the measuring arc, it served 
the same purpose as the mark in line with the pointer, and the 
latter could now be omitted. 

The final machine then consists simply of a revolving die 
which, as shown in Fig. 8, consists of a graduated and pro- 
gressively numbered dial, having a pointer revolving in line 
with the zero, and the machine has a platen consisting of an 



1906.] PRINDLE: THE ART OF INVENTING. 475 

inner circular portion over the pointer and an annular portion 
over the dial, each portion being operated by a separate handle 
so that the dial can be printed at the beginning of the period 
and the pointer alone, at its close. 

The final record has an initial imprint of the dial. Fig. 9a, 
the zero of the dial showing the position of the pointer at the 
beginning of the period, and a final imprint of the pointer alone, 
as shown in Fig. 9b, the complete final record, Fig. 9c, consisting 
of the superimposition of these two records, and showing the 
pointer in line with that graduation whose number is the value 
of the period. Here is a record not only involving no sub- 
traction and no uncertainty but not even, counting in its record, 



\ 



X 



III 

Fig. 6. 
Dial moved up to initial position of zero mark. Elapsed time, 11 
minutes. No subtraction, no counting, no uncertainty; but only one 
record possible at a tirne. 



and, as it was made without disturbing the motions either of the 
pointer or dial, any number of records of other periods could 
have been begun or finished while the machine was measuring 
the period in question. 

Hiding all the intermediate steps in the evolution of this 
invention, it seems the result of spontaneous creation, but 
considering the steps in their successive order, it will be seen 
that the invention is an evolution from the time-stamp; that 
logic rendered the effort of the imagination at any one step 
small by comparison, and that the individual steps might be 
well within the capacity of a person to whom the spontaneous 
creation of the final invention might be utterly impossible. 



476 ; PRINDLE: THE ART OF INVENTING. [May 30 

^' A most interesting example of the evolution of an invention 
is that of the cord-knotter of the self-binding harvester. The 
problem here was to devise a mechanism which would take place 






.-■ 



^>* 



Fig. 7. 
Dial with pointer at zero revolving together. 

of the human hands in tying a knot in a cord whose ends had 

mechanically been brought together around a bundle of grain. 

The first step was to select the knot which could be tied 





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Fig. 8. 

Dial with pointer at zero revolving together, zero mark on pointer 

being replaced by zero of dial. 

by the simplest motions. The knot which the inventor selected 
is that shown in Fig. 10, and is a form of bow-knot. 

The problem was to find how this knot could be tied with 
the smallest number of fingers, making the smallest number 



1906.] PRINDLE: THE ART OF INVENTING. 477 

of simple movements. As anyone would ordinarily tie even 
this simple knot, the movements would be so numerous and 
complex as to seem impossible of performance by mechanism. 
The inventor, by study of his problem, found that this knot 
could be tied by the use of only two fingers of one hand, and 







5 



4' ^ ' /- 






•s 



^ 



to 



/ \^ 



0^ 







Fig. 9a. Fig. 9b. 

Initial Imprint. Final Imprint. 




Fig. 9c. 
Complete Record. 
Simple, direct-reading record. No subtraction, no counting, no uncer- 
tainty. Any number of overlapping periods recorded on one machine. 

by very simple movements. The knot will best be understood 
by following the motions of these fingers in tying the knot. 
Using the first and second fingers of the right hand, they are 
first swept outward and backward in a circular path against 
the two strands of the cord to be tied, as shown in Fig. 11. 



478 



PRINDLE: THE ART OF LN VENTING. 



[May 30 



The fingers continue in their circular motion backward, so 
that the strands of the cord are wrapped around these fingers, 
as shown in Fig. 12. 

Continuing their circular motion, the fingers approach the 
strands of the cord between the twisted portion and a part of 
the machine which holds the ends of the cord, and the fingers 
spread apart as shown in Fig. 13, so that they can pass over 




Fig. 10. 



and grasp the strands thus approached, as shown in Fig. 14. 

The fingers then draw back through the loop which has been 
formed about them, the fingers holding the grasped portion of 
the strands, as shown in Fig. 15. 

The knot is finished by the completion of the retracting 
movement of the fingers through the loop, thus forming the bow 
of the knot as shown in Fig. 16. 



1906.1 



PRiNDLE: THE ART OF INVENTING. 



479 



The inventor found that one finger could have a purely 
rotary movement, as if it were fixed on the arm and unable to 
move independently of the arm, and the movement being as if 
the arm rotated like a shaft, but the second finger must be 
further capable of moving toward and from the first finger 
to perform the opening movement of Fig. 13, and the closing 
movement of Fig. 14 by which it grasps the cord. The in- 
ventor accordingly, from his exhaustive analysis of his problem, 




Fig. 11, 



and his invention or discovery of the proper finger motions, 
had further only to devise the very simple mechanical device 
illustrated in Fig. 17 to replace his fingers. 

The index finger of the hand is represented by the finger S, 
which is integral with the shaft V. The second finger of the 
hand is represented by the finger U , which is pivoted to the 
first finger by the pin s. The grasping movement of the finger 
U is accomplished by a spring V bearing on the shank U\ 



480 



PRINDLE: THE ART OF IX VENTING. 



; Mav 30 



and its opening movement is caused by the travel of an anti- 
friction roll U'\ on the rear end of the pivoted finger, over a 
cam V'\ on the bearing of the shaft. The shaft is rotated by 
the turning of a bevel pinion W on the shaft through the action 
of an intermittent gear. The necessity of drawing the fingers 
backward to accomplish the movement between Figs. 14 and 16 
was avoided by causing the tied bundle to have a motion away 




Fig. 12. 



from the fingers as it is expelled from the machine, the relative 
motion between the fingers and the knot being the same as if 
the fingers drew back. 

Thus the accomplishment of a seemingly almost impossible 
function w^as rendered mechanically simple by an evolution 
from the human hand 
analysis of the conditions involved 



after an exhaustive and ingenious 



1906. 



PRINDLE: THE ART OF INVENTING. 



481 



It will be seen from the examples I have given that the con- 
■structive part of inventing consists of evolution, and it is the 
association of previously known elements in new relations (using 
the term elements in its broadest sense). The results of such 
new association may, themselves, be treated as elements of 
the next stage of development, but in the last analysis nothing 
is invented or created absolutely out of nothing. 




Fig. 13. 



It must also be apparent, that pure reason and method, 
while not taking the place of the inventive faculty, can clear 
the way for the exercise of that faculty and very greatly reduce 
the demands upon it. 

Where it is desired to make a broadly new invention on 
fundamentally different lines from those before — having first 
studied the art to find the results needed, the qualities of 
the material or other absolutely controlling conditions should 



482 



PRIXDLE: THE ART OF LWEXTLXG. 



[May 30 



be exhaustively considered; but at the time of making the 
inventive effort, the details should be dismissed from the mind 
of how results already obtained in the art were gotten. One 
should endeavor to conceive how he would accomplish the 
desired result if he were attempting the problem before any 
one else had ever solved it. In other words, he should endeavor 
to provide himself with the idea elements on which the im- 




FiG. 14. 



agination will operate, but to dismiss from his mind as much 
as possible the old ways in which these elements have been 
associated, and thus leave his imagination free to associate 
them in original and, as to be hoped, better relations than before. 
He should invent all the means he can possibly invent to accom- 
plish the desired result, and should then, before experimenting, 
go to the art to see whether or not these means have before 



1906. 



PRIMDLE: THE ART OF INVENTING. 



483 



been invented. He would probably find that some of the 
elements, at least, have been better worked out than he has 
worked them out. Of course, mechanical dictionaries, and 
other sources of mechanical elements and movements . will be 
found useful in arriving at means for accomplishing certain of 
the motions, if the invention be a machine. Many important 
inventions have been made by persons whose occupation is 




Fig. 15. 



wholly disconnected with the art in which they are inventing, 
because their minds were not prejudiced by what had already 
been done. While such an effort is likely to possess more orig- 
inality than that on the part of a person in the art, there is, of 
course, less probability of its being thoroughly practical. The 
mind well stored with the old ways of solving the problem will, 
of course, be less likely to repeat any of the mistakes of the 
earlier inventors, but it will also not be as apt to strike out on 



484 



PRIXDLE: THE ART OF LWEXTIXG. 



[May 30 



distinctly original lines. It is so full, already, of the old forms 
of association of the elements as to be less likely to think of 
associating them in broadly new relations. 

Nothing should be considered impossible until it has been con- 
clusively worked out or tried by experiments which leave no 
room for doubt. It is no sufficient reason for believing a thing 
won't work because immemorial tradition, or those skilled in 




Fig. 16. 



the art, say it will not work. Many an important improvement 
has been condemned as impracticable, by those in the art, 
before it has been tried. 

A conception which an inventor has been striving for un- 
successfully will sometimes come to him at a time of unaccus- 
tomed mental stimulation. The slight stimulation of the 
movement of a train of cars, and the sound of music, have 



1906.1 



PRIXDLE: THE ART OF IXVEXTLVG. 



485 



been known to produce this effect. The sub-conscious mind, 
after having been prepared by a full consideration of the problem 
to be solved, will sometimes solve the problem without con- 
scious effort, on the part of the inventor. 




Fig. 17. 
The essential parts of the cord-knotter. 



In inventing a machine to operate upon any given material, 
the logical way is to work from the tool to the power. The 
tool or tools should first be invented, and the motions determined 
which are to be given to them. The proper gearing or parts 



486 PRINDLE: THE ART OF INVENTING. [May 30 

to produce from the power each motion for each tool should 
then be invented. It should then be considered if parts of 
each train of gearing cannot be combined, so as to make one 
part do the work of a part in each train; in short, to reduce 
the machine to its lowest terms. Occasionally a mechanism 
will be invented which is exceedingly ingenious, but which it 
is afterwards seen how to simplif}^ greatly at the expense of 
its apparent ingenuity. This simplification will be at the sacri- 
fice of the pride of the inventor, but such considerations as cheap- 
ness, durability and certainty of action leave no choice in the 
matter. It will sometimes be found that a single part can be 
made to actuate several parts, by the interposition of elements 
which reverse the motion taken from such part, or which take 
only a component of the motion of such part, or the resultant 
of the motion of such part and some other part. Where a 
machine involves the conjoint action of several forces, it can 
be more thoroughly studied, if it is found there are positions 
of the machine in which one force or motion only is in operation, 
the effect Cf the others in such position being eliminated, and 
thus the elements making up the resultant effect can be in- 
telligently controlled. 

The drawing board can be made a great source of economy 
in producing inventions. If the three principal views of all 
the essentially different positions of the parts of a machine are 
drawn, it will often be found that defects will be brought to 
light which would not otherwise have been observed until 
the machine was put into the metal. 

It is desirable to see the whole invention clearh^ in the mind 
before beginning to draw, but if that cannot be done, it is 
often of great assistance to draw what can be seen, and the 
clearer perception given by the study of the parts already drawn, 
assists the mind in the conception of the remaining parts. 

If the improvement which it is sought to make is a process, 
it should first be considered whether any radically different 
process can be conceived of, and if so, whether or not it is better 
than the old process, and the reason for its defects, and whether 
it is possible to cure those defects. If the old process appears 
to be in the right general direction, it should be considered 
whether one of the old steps cannot with advantage be replaced 
by a new one, or whether the order of performing the steps cannot 
be changed to advantage. I have in mind one process in which 
a reversal of the order of steps resulted in giving the product 



1906.] PRINDLE: THE ART OF INVENTING. 487 

certain desirable qualities which had before been sought for, 
but could not be obtained. 

It is sometimes desirable not only to invent a good process 
of producing a product, but to control all feasible processes 
of producing the product. Such a case occurred where the pro- 
duct itself had been patented, and it was desirable to extend 
the monopoly be^^ond the time when the patent on the product 
should expire. There were two steps or operations which were 
essential to the production of the product, and the inventor, 
by reference to permutations, saw that there were but three 
orders in which those steps could be performed; first, the order 
K-^, then the order B-A, and then both steps together. The 
order A-B was the old order, which did not produce an article 
having the desired qualities. The inventor therefore, pro- 
ceeded to invent ways by which the steps could be performed 
together, and then by which they could be performed in the 
reverse order, and the patenting such two processes would cover 
generically all possible ways of making the article and secure 
the desired result of putting himself in position to control the 
monopoly after the patent on the article had expired, because 
no one could make the article without using one of his two 
processes. 

In inventing compositions of matter there is one inventor 
who, if he is seeking for a certain result, will take a chemical 
dictionary and make every possible combination of every sub- 
stance that could b}^ any possibility be an ingredient of that 
which he desires to produce. It is as if he were seeking to 
locate a vein of mineral in a given territory, and, instead of 
observing the geographical and geological formation, and thus 
seeking to arrive at the most probable location of the vein, he 
should dig up every foot of earth throughout the whole terri- 
tory, in order finally to locate the vein. This method is ex- 
ceedingly exhaustive, but does not appeal to one as involving 
much exercise of the inventive faculties. 

Inventing has become so much of a science, that if one is 
willing to spend sufficient time and money to enable a com- 
petent corps of inventors to go at the matter exhaustively, 
almost any possible invention involving but a reasonable 
advance in the art can be perfected. 



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